Data set: Monthly averaged RACMO2.3p2 variables; Antarctica
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This is a data set of monthly averaged variables simulated by the hydrostatic regional atmospheric climate model RACMO2.3p2 over Antarctica. At the lateral and ocean boundaries the model is forced by ERA5 reanalysis data every 3 hours from 1979-2022. The model is run at a horizontal resolution of 27 km and 40 vertical levels for the entire Antarctic ice sheet, which constitutes an update of the simulation forced from 1979-2018 by ERA-Interim reported in van Wessem et al., 2018. Upper air relaxation of wind, humidity and temperature is also active (Van de Berg et al., 2016). This version of the model is specifically applied to the polar regions by interactive coupling to a multilayer snow model that calculates melt, refreezing, percolation and runoff of meltwater (Ettema et al., 2010). In addition, snow albedo is calculated through a prognostic scheme for snow grain size (Kuipers Munneke et al., 2011) while a drifting snow scheme simulates the interaction of the near-surface air with drifting snow (Lenaerts et al., 2010). This dataset is provided on a rotated polar coordinate grid. In such a rotated pole projection the grid is defined over the equator and then rotated to the area of interest. One of the advantages is that the grid distance can be defined in fraction of degrees, which results in near equidistant grid cells as long as the domain is small enough, and provides the most accurate model calculations. However, re-projecting these data on other grids is often troublesome, as after rotation the grid is non-equidistant and most software packages cannot directly handle this. Stef Lhermitte provided a nice solution for reprojecting the RACMO data on his gitlab-page: https://gitlab.tudelft.nl/slhermitte/manuals/blob/master/RACMO_reproject.md. The dataset includes the following surface- and atmospheric variables. Additional variables and higher temporal resolutuon up to 3 hourly are available on request: Surface mass balance (SMB) variables (in kg m-2 mo-1 or mm water equivalent mo-1) smb : (Specific) Surface mass balance defined as SMB = Total precipitation + sublimation - runoff snowmelt : Surface snowmelt production refreeze : Refreezing of meltwater snowfall : Solid precipitation precip : Total precipitation (snowfall + rainfall); to calculate rainfall use rainfall = precip - snowfall runoff : Surface meltwater runoff subl : Snow sublimation (including sublimation of drifting snow). Negative values are sublimation, positive values are snow deposition. erds : erosion of drifting snow Atmospheric variables t2m : 2-m Temperature q2m : 2-m Specific humidity rh2m : 2-m Relative humidity (RH) tskin : Surface/skin temperature. Calculated from closing the surface energy budget. psurf : Surface pressure u10m : Zonal wind speed at 10 m v10m : Meridional wind speed at 10 m ff10m : Wind speed at 10 m u0500 : Zonal wind speed at 500 hPa v0500 : Meridional wind speed at 500 hPa z0500 : Geopotential height at 500 hPa Surface Energy Budget (SEB) variables (in J m-2); SEB = LWnet+SWnet+SHF+LHF+GHF Values are monthly cumulative: to convert to W m-2 divide by amount of seconds in a month: 30*24*3600. lwsn : Net longwave radiation (LWnet=LWdown-LWup) swsn : Net shortwave radiation (SWnet=SWdown-SWup) lwsd : Downwelling longwave radiation at the surface swsd : Downwelling shortwave radiation at the surface swsu : Upwelling shortwave radiation at the surface senf : Upward Sensible Heat Flux (SHF) at the surface latf : Upward Latent Heat Flux (LHF) at the surface (our simulated LHF doesn't explicitly close the SEB, as it also includes in-air sublimation, but the effect should be rougly neglible) gbot : Soil/Ground Heat Flux (GHF) Snow variables totpore : Vertically integrated pore space (m) totwat : Total liquid water content of the snowpack (kg m-2) zsnow : Total snowpack thickness (m) Grid, elevation, coordinates and masks in Height_latlon_ANT27.nc (240 by 262 grid boxes) mask2d : Full ice mask fraction (grounded ice + floating ice shelves) [0..1] maskgrounded2d : Grounded ice sheet mask fraction [0..1] height : Surface elevation (m) slope : Surface slope (m m-1) aspect : Direction of surface slope (degrees) lat : Latitude (polar) lon : Longitude (polar) Ice shelf and ice sheet drainage basins mask in TotIS_RACMO_ANT27_IMBIE2.nc This file contains masks on the RACMO grid for the drainage basins as defined in http://imbie.org/imbie-3/drainage-basins/ (Rignot et al., 2013, IMBIE2, IMBIE3), including masks seperately for the ice shelves they drain into, numbered counterclockwise from 0 to 18. mask2dF : Full ice mask including ice shelves IceShelves : Ice shelf masks GroundedIce : Grounded ice sheet drainage basins
本数据集为由静力区域大气气候模型RACMO2.3p2在南极地区模拟得到的月均变量数据集。模型的侧边界与海洋边界由1979-2022年间每3小时一次的ERA5再分析数据强迫驱动。该模型以27公里的水平分辨率与40层垂直层数运行，覆盖整个南极冰盖，是对van Wessem等人2018年发布的、使用ERA-Interim强迫的1979-2018年模拟的更新版本。风、湿度与温度的高空松弛方案（Van de Berg等，2016）亦已启用。 此版本模型通过与多层雪模型交互式耦合，专门应用于极地地区：该雪模型可计算融水的融化、再冻结、渗透与径流过程（Ettema等，2010）。此外，积雪反照率通过积雪粒径的预报方案计算（Kuipers Munneke等，2011），同时采用吹雪方案模拟近地表空气与吹雪的相互作用（Lenaerts等，2010）。 本数据集采用旋转极坐标网格存储。此类旋转极投影网格首先在赤道上定义，随后旋转至目标研究区域。其优势之一是网格距离可按度数分数定义，只要研究区域足够小，即可获得近似等距的网格单元，从而实现最精准的模型计算。但将此类数据重投影至其他网格通常较为困难，因为旋转后的网格并非等距，且多数软件包无法直接处理。Stef Lhermitte在其GitLab页面提供了RACMO数据重投影的便捷解决方案：https://gitlab.tudelft.nl/slhermitte/manuals/blob/master/RACMO_reproject.md。 本数据集包含以下地表与大气变量，额外变量与更高时间分辨率（最高3小时）的数据可按需申请： ### 表面质量平衡（Surface Mass Balance, SMB）变量（单位：kg m⁻² mo⁻¹ 或 mm水当量 mo⁻¹） smb：（比）表面质量平衡，定义为 SMB = 总降水 + 升华 - 径流融雪 snowmelt：地表融雪产水量 refreeze：融水再冻结量 snowfall：固态降水 precip：总降水（降雪+降雨）；若需计算降雨量，可使用 rainfall = precip - snowfall runoff：地表融水径流 subl：积雪升华（包括吹雪的升华）。负值代表升华，正值代表积雪沉积。 erds：吹雪侵蚀量 ### 大气变量 t2m：2米气温 q2m：2米比湿 rh2m：2米相对湿度（RH） tskin：地表/表皮温度，通过闭合地表能量预算计算得到 psurf：地表气压 u10m：10米纬向风速 v10m：10米经向风速 ff10m：10米风速 u0500：500百帕纬向风速 v0500：500百帕经向风速 z0500：500百帕位势高度 ### 地表能量预算（Surface Energy Budget, SEB）变量（单位：J m⁻²） 地表能量预算公式为 SEB = LWnet + SWnet + SHF + LHF + GHF，所有变量数值均为月累积量：若要转换为瓦每平方米（W m⁻²），需除以当月总秒数（30×24×3600）。 lwsn：净长波辐射（LWnet = LWdown - LWup） swsn：净短波辐射（SWnet = SWdown - SWup） lwsd：地表向下长波辐射 swsd：地表向下短波辐射 swsu：地表向上短波辐射 senf：地表向上感热通量（SHF） latf：地表向上潜热通量（LHF）（本研究模拟的潜热通量未显式闭合地表能量预算，因其还包含空气中的升华过程，但该影响大致可忽略不计） gbot：土壤/地表热通量（GHF） ### 积雪变量 totpore：垂直积分孔隙空间（单位：m） totwat：积雪层总液态水含量（单位：kg m⁻²） zsnow：总积雪厚度（单位：m） ### 网格、高程、坐标与掩膜数据 存储于Height_latlon_ANT27.nc（包含240×262个网格单元）： mask2d：全冰盖掩膜分数（接地冰盖+浮动冰架）[0..1] maskgrounded2d：基岩冰盖掩膜分数 [0..1] height：地表高程（单位：m） slope：地表坡度（单位：m m⁻¹） aspect：地表坡向（单位：°） lat：极地纬度 lon：极地经度 ### 冰架与冰盖排水盆地掩膜 存储于TotIS_RACMO_ANT27_IMBIE2.nc，该文件包含RACMO网格上的排水盆地掩膜，其定义源自http://imbie.org/imbie-3/drainage-basins/（Rignot等，2013，IMBIE2、IMBIE3），包括各自对应注入冰架的掩膜，按逆时针方向从0编号至18。相关变量包括： mask2dF：包含冰架的全冰盖掩膜 IceShelves：冰架掩膜 GroundedIce：基岩冰盖排水盆地
